Core 4 is the Molecular Core. It serves as the central resource for the projects that isolate and process RNA on Affymetrix microarrays, and for performing RT-PCR confirmation of the microarray data for those projects. The UCD Affymetrix Core Facility is run by Dr. Jeffrey Gregg and is equipped with fluidics stations, hybridization ovens, and the new scanner required to scan the human Affymetrix U133 2.0PLUS arrays. Preliminary data from the previous CHARGE study has shown that there are changes in gene expression in the blood of children with autism compared to control children in the general population (GP) and to control children with mental retardation and developmental delay (MR/DD). The blood genomic profile in children with autism without regression (A) was different from controls, autism spectrum disorder (ASD) and different from children with autism with regression (A-R). In addition, there is a group of regulated genes in most children with A, A-R and with ASD that are expressed by natural killer (NK) cells in peripheral blood, suggesting an abnormality in this cell type that is common to all types of autism. These NK-cell related genes are expressed by all of the autism phenotypes including A, A-R and ASD, and hence may point to common pathways that underlie the common language and behavioral abnormalities in all three disorders. This core will be utilized by the projects as follows. Project #1: Aim #1: Perform genomic (RNA expression on microarrays) studies on blood from children with autism in the 4-9 year old range, and compare to the blood genomic profiles we have obtained in children with autism in the 2-5 year old age range. Aim #2. Compare gene expression as a function of blood metal levels in both age groups in A, A-R, ASD, MR/DD and GP groups. Aim #3. Examine genomic profiles in pregnant mothers who have previously given birth to an autistic child to determine if there is a specific genomic profile that correlates with whether the mother's fetus is destined to develop autism. Project #2. Aim #1. Describe the gene expression profiles in the blood using specific white blood cell subsets including NK cells for children with autism without regression, autism with regression, and ASD children compared to GP and delayed children. Aim #2. Examine gene expression following stimulation or activation of specific white blood cell subsets of A, A-R, ASD, MR/DD and GP children with: low level mercury;immune cell stimulation/activation with vaccine antigens and cell-specific mitogens;and xenobiotics. Project #3. Compare gene expression profiles in the blood of children with autism to the blood of experimental animals exposed to toxicants including organic mercury, PCB 95, and PBDE 47 (Project #3).